Safe load indicating devices for cranes



Sept. 15, 1964 R. 1.. AITKEN 3,148,659

SAFE LOAD INDICATING DEVICES FOR CRANES Filed Feb. 4, 19s: 5 Sheets-Sheet 1 //VVENTOE wp PM ATTORA/E)? Sept. 15, 1964 R. L. AITKEN 3,143,659

.SAFE.LOAD INDICATING DEVICES FOR CRANES File'd Feb. 4, 1965 3 Sheets-Sheet 2 Fig 3.

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Sept. 15, 1964 R. L. AITKEN 3,148,659

SAFE LOAD INDICATING DEVICES FOR CRANES Filed Feb. 4, 1963 3 Sheets-Sheet 3 United States Patent 3,148,659 SAFE LOAD HNDHCATING DEVICES FOR CRANES Robert London Aitken, 5t) Pall Mall, London, England Filed Feb. 4, 1963, Ser. No. 255,969 Claims priority, application Great Britain Feb. 9, 1962 8 Claims. (Cl. 116-124) The present invention relates to safe-load indicating devices for cranes and the like, more particularly to de vices for deriving the effective working radius to be used in safe-load indicators on cranes with extendable jibs.

It is common practice to construct a safe-load indicating device with automatically acting compensating means to ensure that the safe-load indicating device indicates a safe-load correctly at different crane radii of operation. Such compensation is commonly effected by taking a measurement of angular movement derived from the movement of the jib in relation to a fixed part of the machine.

Such arrangement operates satisfactorily when the jib length of the machine is constant, but does not operate with cranes having extending jibs, for example, jibs having a movable peak portion which can move longitudinally in relation to the bottom portion of the jib. In such cases it is not possible to determine the efiective radius of the crane by measuring the angle of the jib or of any associated part alone.

It is an object of this invention to provide an effective crane radius device, for use on cranes having extending jibs for introducing a compensating factor into a crane safe-load indicating device, which is itself automatically compensated by change of jib angle. In this device the angle of the jib and the position of its extending portion are compounded to provide a movement which is applied to the means by which the safe-load indicator is compensated for change of jib angle and this compounded movement compensates the safe-load indicator for change of the true operating radius of the crane.

Since safe-load indicating devices for fixed-length jib cranes are well-known and relatively standardised units it is more convenient to compensate them against changes of jib length than it is to manufacture a special safe-load indicating device for variable-length jib cranes.

Accordingly, the present invention provides an effective crane radius device for compensating a safe-load indicating device of the type which is compensated for change of operating radius by measurement of the angular position of the jib or of a part associated therewith comprising an output member to be connected by a linkage to the jib angle compensating means of the safe-load indicating device, the spatial position of the point of connection between said output member and said linkage being a function of the jib angle of the crane and the eifective length of the jib.

Conveniently, the effective jib crane radius device comprises an output member and two input members respectively movable in response to change of jib angle and change of jib extension, means, combining the movement of the two input members, connected with the output member whereby the spatial position of said connection point is a function of the movement of the two input members.

In one preferred form of this invention said output member is mounted on two pivots, said pivots being angularly movable relative to each other and likewise being movable relative to each other lengthwise of the output member, means responsive to change of jib extension causing relative movement between said pivots lengthwise of the output member so that their relative distance from one another is a function of the jib extension, means responsive to change of jib length causing relative anguin movement of said pivots so that the relative angular position of said pivots is a function of the jib angle.

In another form of this invention the output member is pivoted on a fixed pivot and has'a second pivotmovable along a track lengthwise of said output member and comprising means for moving said second pivot along said track so that its distance from the first pivot is a func tion of the jib extension and means connecting said second pivot to a point on a lever pivoted to a fixed point, movement responsive to changes of jib angle being imposed on said lever.

In some known safe-load indicating devices the compensation of the device for change of effective operating radius is effected by moving a roller or a fulcrum in a multiple lever system so as to vary the angular movement imparted to one lever by a given angular movement of a second lever. Examples of safe-load indicating devices of this kind are described in'British Patent No. 723,070 and in my co-pending Patent Application Ser. No. 256,- 029, now US. Patent 3,123,814. In both these examples the position of the movable fulcrum is automatically adjusted by rotation of a cam, which is caused to assume a position which corresponds to the particular angle of the jib and is thus a measure of the true opera-ting radius of the crane when the eifective length of the jib is constant. It is a purpose of the present invention to provide a movement obtained by compounding the jib angle and the jib extension and apply this movement to a member used as a means of rotating the cam in these types of indicators.

Where angular movement of the jib is produced by a hydraulic ram, it is desirable to transmit to the safe-load indicator a crane force, which is not just a measure of the hydraulic pressure in the'ram but is a measure of the moment of the ram-force about thejib foot pin. A subsidiary feature of the invention is to combine the elfective crane radius device of the present invention with a crane load compensating device which compounds the pressure of a hydraulic ram, forming the derricking means of the jib, with the jib angle so as to form a convenient measure of the moment of the ram about the jib foot pm.

According to this aspect of the invention a crane load compensating device for a crane having a jib which is moved angularly in the vertical plane by a hydraulic ram comprising an operating member mounted on two pivots, said pivots being angularly movable relative to each other, and said pivots being movable relative to each other lengthwise of said operating member, means responsive. to

change of jib angle causing relative movement between said pivots lengthwise of the operating member so. that their relative distance from one another is a function of the jib angle, means responsive to change of ram pressure causing relative angular movement of said pivots so that such relative angular position is a function of the ram pressure.

The invention is hereinafter further described, by way of example, with reference tothe following drawings in which:

FIG. 1 shows a side elevation of one formof effective radius device of the invention,

FIG. 2 shows a side elevation of another form of effective radius device,

FIG. 3 is a section along the line IIIIII of FIG. 2,

and

cam 2, both of which are keyed to a shaft 3 mounted in an indicatorbox 4. A lever 5, pivotally mountedrin the box 4 on a pivot 6, carries a cam follower 7 which bears 3 against the face of cam 2. At the other end of the lever 5 there is mounted, on a pivot pin 8, a lever 9, which constitutes the output member.

A link is moved in response to movement of the extension length of the jib and is connected by a lever 10a to a cam 11, both of which are keyed to a shaft 12 mounted in the box 4. A pair of parallel bell crank levers 13 are pivotally mounted in the box 4 on a pivot 14 and carry a cam follower 15 which bears upon the face of the cam 11. The ends of the other arms of the bell crank levers 13 are connected by a cross head 16. The bell crank levers 13 are also connected to a spring 19 at an anchorage 20 and the other end of the spring is connected at a point 21 to the indicator box 4.

The cross head 16 constitutes a pivot movable lengthwise in a slot 18 in the output member 9. A cable 22 is connected at a point 23 to the output member 9 and the cable is slidably carried in a sheath 24 fixed to the indicator box 4 by a clip 25. A spring 26 is fixed to the output member 9 at a point 27 to hold the cam follower 7 against cam 2 and keeps taut the cable 22.

In operation change of jib angle causes cam 2 to turn and change of jib extension causes cam 11 to turn. Cam 11 is cut so that the cross head 16 is moved in such manner that its distance from the pivot 8 is inversely related to the eifecitve length of the jib. The cam movements change the positions of pivot pin 8 and the cross head 16 relative to one another both angularly and lengthwise of the output member 9. The changes of the position of the two pivots are compounded in the output member and vary the position of the point 23 to which cable 22 is connected. The movement of cable 22 is applied to a safe-load indicator box (not shown) for example the safe load indicator box illustrated in my copending patent application Ser. No. 256,029, now US. Patent 3,123,814, and is connected to a member of that device through which it is compensated for change of jib angle. The other input member of the safe-load indicator device will have a crane loading applied thereto in the normal manner.

In the effective radius device shown in FIGS. 2 and 3 change of jib angle moves link 31, which is connected by lever 31a to a cam 32 both of which are keyed on the shaft 33 mounted in a box 34. A lever 35 pivotally mounted in the box 34 on a pivot pin 36 carries a cam follower 37 which bears on the face of cam 32. A spring 38 is connected to the lever 35 at a point 39 and the other end of the spring 38 is mounted on the box at a point 40 to hold the cam follower 37 on the face of the cam 32. j

A link 41 responsive to movement of the extension length of the jib is connected to a lever 41a to turn a cam 42, the lever and cam being keyed on a shaft 43 mounted in the box 34. A cam lever 44 carries a cam follower 45 which bears on the face of the cam 42, and is keyed to a shaft 46, on which is also keyed a lever 47. At a point 48 on the lever 47 there is connected a cable 49 which extends through a guideway in a bell crank lever 50, which constitutes the output member. The lever 58 is pivotally mounted in the box 34 on a pivot pin 51. On one arm of the bell crank lever 50 is slidably mounted a cross head 52 which is pivotally connected at 55 to a link 53, which is connected by a pivot pin 54 to lever 35. The cable 49 extending from point 48 on lever 47 is connected to the cross head 52 and passes over a pulley 56 mounted on a shaft 57 and arranged so that the cable passes substantially through the axis of pivot 51 so that tilting of the lever 50 does not of itself cause movement of the cross head 52. A helical spring 58 mounted on the bell crank lever 50 holds the cable 49 taut.

In operation the cam 32 is moved in accordance with change of jib angle and the cam 42 is moved in response to change of jib extension, change of jib angle causing the cross head 52 to move angularly about the fixed pivot 51. Change of jib extension causes the cross head 52 to move lengthwise of the arm of the bell crank lever 50 on which it is mounted. These movements are compounded by the bell crank lever and cause arm 59 of the bell crank lever to move link 60 which is connected to the arm 59 by a pivot pin 61. The link 60 is again connected to the angle compensation input of a safe-load indicator.

In FIG. 4 there is shown a device which is intended for connection to the load input of a safe-load indicator, which is also being compensated by a device of the type shown in FIGS. 13. The device of FIG. 4 is intended for use in a crane, the jib of which is supported by a hydraulic ram, the angle of which in the vertical plane varies with change of jib angle. In this device a pipe 71 connects the hydraulic ram to a cylinder 72 carrying a piston 73 and mounted on a box 74. A piston 73 acts against a restoring spring 75 located between the piston and box 74 and thus the position of the piston in its cylinder is a measure of the ram pressure. A lever 76, pivotally mounted on a pin 76a in the box 74, is connected by a pivot pin 77 to the piston 73. The other end of the lever 76 is connected by a pivot pin 78 to alever 79.

A link 80 which is moved in response to change of ram angle (which is itself related to the jib angle) is connected by a lever 89a to a cam 81 both of which are keyed to a shaft 82 mounted in box 74. A pair of parallel bell crank levers 83 pivotally mounted in box 74 on pivot pin 84 carry a cam follower 85 at one end to follow the face of cam 81 and a pivot 86 at the other end arranged to move in an arcuate slot 87 in the lever 79, which constitutes the output member. A spring 88 connected to the lever 83 and the box 74 holds the cam follower 85 on the face of the cam 81.

A pivot pin 89 in the output member 79 connects a link 90 to the member 79 and the link 90 can be connected to the input force member of a safe-load indicator of the type referred to above.

In operation cam 81 is cut so that any two radians are proportional to the moment arm of the hydraulic ram about the jib foot pin of the crane and thus the moment arm of the pivot 86 about the pivot point 78 of lever 79 will be proportionate to the moment arm of the hydraulic ram about the jib foot pin. Movement of link 90 which is freely pivoted on lever 79 will, therefore, be a combination of the ram pressure represented by the position of piston 73 in its cylinder and of the moment arm of the ram about the jib foot pin. By a suitable choice of the dimensions of the lever 79 and the cam 81 a force on link 90 can always be taken to represent a measure of the product of hydraulic pressure and moment arm of the ram and therefore of the product of load and radius regardless of the combination of the jib angle and jib extension by which that radius is reached.

Iclaim:

1. An effective crane radius device for compensating a safe-load indicating device of the type which is compensated for change of operating radius by compensating means which are incorporated in the safe-load indicating device in accordance with a change of the vertical angular position of a part of the crane, which part changes its angle to the vertical simultaneously with change of the vertical angular position of the jib, said device comprising a body, an output member movable in said body, a transmission linkage at a connection point on said output member and adapted to be connected to the jib angle compensating means of the safe-load indicating device, a first input member movable in said body in response to change of crane jib angle, a second input member movable in said body in response to change of crane jib extension, and combining means coupled to said input members and connected with the output member for combining the movement of said first and second input members, whereby the spatial position of said connection point, at which said output member and said transmission linkage are connected is a function of the movement of the first and second input members.

2. An effective crane radius device as claimed in claim 1 in which said combining means includes two pivots and said output member is mounted on said two pivots, said pivots being angularly movable relative to each other, and likewise being movable relative to each other lengthwise of the output member, and said combining means further includes means responsive to the movement of said second input member on change of jib extension causing relative movement between said pivots lengthwise of the output member so that their relative distance from one another is a function of the jib extension, and said combining means further includes means responsive to the movement of said first input member on change of jib length due to a change in jib angle causing relative angular movement of said pivots so that the relative angular position of said pivots is a function of the jib angle.

3. An eifective crane radius device as claimed in claim 2, in which said means responsive to the movement of said first input member comprises a lever pivotally mounted in said body, and said first input member comprises means for tilting said lever about its pivotal mounting in response to change of crane jib angle, said lever being pivotally connected to said output member at one of said pivots, and said means responsive to the movement of said second input member comprises a second lever pivotally mounted in said body, and said second input member comprises means for tilting said second lever about its pivot in response to change of crane jib extension, said second lever being connected to said output member at the other of said pivots, said other pivot being movable longitudinally of the output member.

4. An effective crane radius device as claimed in claim 1, in which said body has a fixed pivot on which the output member is pivoted, a track extending lengthwise of said output member, a second pivot movable along said track, said combining means including means connected between said second pivot and said first input member for moving said second pivot along said track in response to movement of said second input member so that the distance of said second pivot from the fixed first pivot is a function of the jib extension, and said combining means further including a lever pivoted on said body, means connecting said second pivot to a point on said lever, and means coupled between said first input member and said lever for tilting said lever in response to said first input member.

5. An efiective crane radius device as claimed in claim 4, in which means for moving said second pivot along said track comprises a further lever pivotally mounted at one end, a cam follower on said further lever, and said second input member is a cam movable in response to change of jib extension and on which said cam follower bears, and a linkage connecting the end of said further lever remote from its pivot with the second pivot.

6. An effective crane radius device as claimed in claim 5, in which the linkage is in the form of an inextensible flexible member, a guideway in said output member along which said flexible member passes, a member supporting said second pivot and movable lengthwise of said output member and to which said flexible member is connected, and means acting on said linkage for keeping said inextensible, flexible member taut.

7. An effective crane radius device for compensating a safe-load indicating device of the type which is compensated for change of operating radius by compensating means which are incorporated in the safe-load indicating device in accordance with a change of the vertical angular position of a part of the crane, which part changes its angle to the vertical simultaneously with a change of the vertical angular position of the jib, said device being for a crane having a jib which is moved angularly in the vertical plane by a hydraulic ram, said device comprising a body, an output member movable in said body, a transmission linkage at a connection point on said output member and adapted to be connected to the jib angle compensating means of the safe-load indicating device, a hydraulic pressure responsive input member movable in said body in response to change of crane jib angle, a second input member movable in said body in response to change of crane jibextension, and combining means coupled to said input members and connected with the output member for combining the movement of said first and second input members, said hydraulic pressure responsive input member being adapted to be coupled to the hydraulic ram for moving the jib angularly, whereby the spatial position of said connection point, at which said output member and said transmission linkage are connected is a function of the movement of the hydraulic pressure responsive and second input members.

8. An effective crane radius device as claimed in claim 7 in which said hydraulic pressure responsive input member comprises a cylinder mounted on said body, and a piston and a restoring spring in said cylinder, and said combining means includes a lever pivotally mounted in said body to one end of which said piston is connected, and having the other end pivotally connected to said output member. 5

References Cited in the file of this patent UNITED STATES PATENTS 1,795,405 Nash Mar. 10, 1931 2,030,529 Nash Feb. 11, 1936 2,988,040 Aitken June 13, 1961 

1. AN EFFECTIVE CRANE RADIUS DEVICE FOR COMPENSATING A SAFE-LOAD INDICATING DEVICE OF THE TYPE WHICH IS COMPENSATED FOR CHANGE OF OPERATING RADIUS BY COMPENSATING MEANS WHICH ARE INCORPORATED IN THE SAFE-LOAD INDICATING DEVICE IN ACCORDANCE WITH A CHANGE OF THE VERTICAL ANGULAR POSITION OF A PART OF THE CRANE, WHICH PART CHANGES ITS ANGLE TO THE VERTICAL SIMULATANEOUSLY WITH CHANGE OF THE VERTICAL ANGULAR POSITION OF THE JIB, SAID DEVICE COMPRISING A BODY, AN OUTPUT MEMBER MOVABLE IN SAID BODY, A TRANSMISSION LINKAGE AT A CONNECTION POINT ON SAID OUTPUT MEMBER AND ADAPTED TO BE CONNECTED TO THE JIB ANGLE COMPENSATING MEANS OF THE SAFE-LOAD INDICATING DEVICE, A FIRST INPUT MEMBER MOVABLE IN SAID BODY IN RESPONSE TO CHANGE OF CRANE JIB ANGLE, A SECOND INPUT MEMBER MOVABLE IN SAID BODY IN RESPONSE TO CHANGE OF CRANE JIB EXTENSION, AND COMBINING MEANS COUPLED TO SAID INPUT MEMBERS AND CONNECTED WITH THE OUTPUT MEMBER FOR COMBINING THE MOVEMENT OF SAID FIRST AND SECOND INPUT MEMBERS, WHEREBY THE SPATIAL POSITION OF SAID CONNECTION POINT, AT WHICH SAID OUTPUT MEMBER AND SAID TRANSMISSION LINKAGE ARE CONNECTED IS A FUNCTION OF THE MOVEMENT OF THE FIRST AND SECOND INPUT MEMBERS. 